For the purpose of improving the reproducibility of continuous gradation dot images or that of line images in the field of graphic arts, image forming systems yielding super-hard photographic characteristics (especially having .gamma. of 10 or more) are needed.
In particular, image forming systems using processing solutions having good storage stability and yielding super-hard photographic characteristics are desired. As one example, systems have been proposed for forming a super-hard negative image having .gamma. of more than 10 by processing a surface-latent-image-forming silver halide photographic material containing a particular acylhydrazine compound with a developer containing a sulfite preservative in an amount of 0.15 mol/liter or more and having pH of from 11.0 to 12.3; examples of such systems are found in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. The new image forming system is characterized in that even photographic materials comprising silver iodobromide emulsions or silver chloroiodobromide emulsions may be processed by the system, while only those comprising silver chlorobromide emulsions with high silver chloride contents can be processed by conventional, super-hard image-forming systems. In addition, since the developer to be used in the new system may contain a large amount of a sulfite preservative, the storage stability of the developer used therein is relatively good, and this is another advantage of the new system, while conventional lith developers can contain only an extremely small amount of a sulfite preservative.
However, the developer having pH of 11 or more, as used in the new system, is easily oxidized with air and is unstable, so that it cannot be stored or used for a long period of time.
Various devices have heretofore been tried for developing silver halide photographic materials containing hydrazine compounds with developers having lower pH values so as to form hard images.
In JP-A-1-179939 and JP-A-1-179940 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), there is described a method of processing a photographic material containing a nucleating development accelerator having an adsorbing group of adsorbing silver halide emulsion grains and a nucleating agent having an adsorbing group of the same kind, with a developer having a pH of not higher than 11.0.
In U.S. Pat. Nos. 4,998,604, 4,994,365 and 4,975,354, there are disclosed hydrazine compounds having ethylene oxide repeating units and hydrazine compounds having pyridinium groups. From the examples thereof, however, the contrast of the images formed by the inventions of the U.S. patents is not sufficient. Therefore, it is difficult to obtain hard images having the necessary Dmax from the photographic materials of the above patented inventions, when the materials are processed under practical processing conditions.
The variation of the photographic properties of nucleating hard photographic materials containing hydrazine derivatives is great, depending upon the change of pH of the developers to be used for processing them. The pH of developers greatly fluctuates due to the aerial oxidation thereof as well the elevation of the thickness thereof by vaporization of water or the lowering of the same by absorption of carbon dioxide in air. Therefore, various devices have been tried for reducing the dependence of photographic properties on the pH of developers.
Examples of using chemically-sensitized silver chlorobromides in photographic systems using hydrazines have been disclosed in, for example, JP-A-53-20921, JP-A-60-83028, JP-A-60-140399, JP-A-63-46437, JP-A-63-103230, JP-A-3-294844, JP-A-3-294845 and JP-A-4-174424 and Japanese Patent Application No. 3-188230. On the other hand, examples of combinations of hydrazines and silver halide emulsions containing heavy metal complexes of, for example, rhodium, iridium or the like have been disclosed in, for example, JP-A-60-83028, JP-A-61-47942, JP-A-61-47943, JP-A-61-29837, JP-A-62-201233, JP-A-62-235947 and JP-A-63-103232.
Various examples of photographic systems containing hydrazines and anion-charged cyanine dyes, such as, for example, alkali salts of 5,5'-dichloro-9-ethyl-3,3'-bis(3-sulfopropyl)oxacarbocyanine have been disclosed, for example, in JP-A-61-29837, JP-A-62-235947, JP-A-62-280733, JP-A-62-280734, JP-A-2-40, JP-A-2-124560, JP-A-2-262653 and JP-A-3-63641.